Geologists Study China Earthquake For Glimpse Into Future

Do not confuse rigid plate tectonics with a suture zone. Shortening of the Asian continent is taking place with this orogeny. It is a fragile and very unstable environment, the collapsing momentum of the Indian content is destined to reek hovac in China for millions of years to come.

The article is interesting, but is really summed up in the final sentence:

<"....The analysis does not say there is going to be an earthquake, just that the potential exists on some of the faults."....">

Now I could have told them all that, without all that study and meeting money being spent.

The Tibetan Plateau located on the Eurasian Plate, is located in central Asia and has a mean elevation exceeding 4000 meters above sea level with an area approximately 2.3 X 106 km².

Now we must remember that huge area was once under the sea, along with the edge of the Eurasian Plate which has buckled up to form the Himalayas.

So, we can estimate that the energy expended in that is unstoppable by any means we know of, and the Indian Plate is still moving at an approximate 1 to 1.5 centimetre per year.

Now that may not sound much, until the total energy input is realised.

At all compressional boundaries, as near the Himalayan Massif, earthquakes are found in several locations ranging from the very near surface to several hundred kilometers depth, because the coldness of the subducting plate permits brittle failure down to as much as 700 km below the surface.

Compressional boundaries do have Earth's largest temblors, with some quakes on subduction zones in Alaska and Chile having exceeded magnitude 9.

Remember the magnitude scale is logarithmic, not linear.

Thus this area, much of which is highly populated, is going to continue to experience major quakes, at irregular intervals, until the opposing plates fully lock, and relative movement ceases, which may perhaps never actually happen.

in other words, the Indian Plate may continue to bulldoze its way through the Eurasian Plate, raising further mountain chains parallel to the Himalayan Alps.The outlook therefore, for that area, is a shaky one.

We have had some very major quakes here in New Zealand, but fortunately the active areas are generally not highly populated.

Kind Regards from "The Shaky Isles"

"Now that may not sound much, until the total energy input is realised."

Boy, you said a mouthful there, Sparky! A conservative estimate of 5 million cubic miles of rock moving at a rate of 1 - 1.5 cm/yr would require HOW much energy input? The mind boggles.

Hi Enviroman,

It's the same with the American plate and the European plate, The UK and USA are moving apart at 1.5cm pr year, and yes there is a powerfull energy input to move two plates apart. This has prduced the mid-Atlantic ridge under the ocean.

Spencer.

Did you know that the MOR was created by rifting of Pangea, the once super continent, and that prior to its creation the Adirondack Mountains mirrored the present collision aforementioned in this blog. The MOR is also at a snails pace as its divergence rate doesn't quite compare to some of the ocean ridges in the Pacific Ocean. Some believe this is due to the plate mass differential and the driving force of slab pull dominating plate tectonics.

<...The UK and USA are moving apart at 1.5cm pr year...>

Some might say, "long may it continue".....

Here's a map of the plates and their movement vectors (courtesy of Wiki), judge for yourself how long it may wave...

The MOR has been spreading at its current rate for roughly 200 million years. Rates and directions can change when continental plates collide and we'd expect there to be a rapid die off in the momentum of the Indian Plate as it gets consumed by the Eurasian Plate... just looks how much bigger the Eurasian plate is.

There are also a myriad of small plates that are not identified by this crude model.

Another interesting aspects to look at is that hot spots, like the one that forms the Hawaiian Islands, can be sued to identify vector changes in plate motion.

look here:

http://www.cliffshade.com/colorado/images/hawaii-emperor.gif

Hello EnviroMan

The battery on my calculator went flat, during my calculations

Kind Regards....

No worries, the display probably won't handle a number that big anyway!

eyes wide shut...

The Eurasian plate is rather massive when compared to the Indian plate. I think we should look at a few historical remnants of orogeny's as observed in North America to understand that at some point momentum will die off. The thickest crustal segment in modern history will slowly subside due to erosion and melting near the moho after the suture zone welds shut, forming some sort of semi-super continent that will exist until active rifting takes place.

As far as the next several million years are concerned the tibetan plateau will suffer from sporadic activity over a rather large area due to the nature of low angle thrust faults analogous to these events.

Please check out the post I labeled

China's Earthquake and the Indus-Yarlung Suture Zone

@ http://cr4.globalspec.com/blog/101/Geological-Factors-in-Engineering

Yes, of course; but contemplating the amount of energy present in that much moving mass is still awe-inspiring.

The tectonic plate motion is driven primarily by the upwelling magma.

As this fuses to the previously upwelled sea-floor plate edge, it cools over time, shrinking in the process.

That means the rift at upwelling points remains open, because of the divergent gap between cooling plate edges.

So all that energy is supplied from sea-floor spreading, in the tandem effects of shrinkage on cooling, plus further magma upwelling to fill the gap, all on a continuing basis.

It's nothing to do with the relative sizes of the tectonic plates, but the temperature differentials at the mid-ocean ridge which drives the plates, and consequently if enough energy is expended at the mid-oceanic ridge, the Tibetan Plateau, plus further all the way to the Arctic ocean, may suffer severe movement in future years.

If you want a "quiet life", it's really best to choose a location where the rocks are well-lubricated, and the major deformation, as in the Supra-Continent of Zealandia, where I live.

Most of Zealandia is under 2kM of seawater.

Kind Regards....

Interesting theory,

I have debated this before, and if you care to do a little research the best supported theories recognize slab pull as the dominant force driving plate tectonics. Last time I debated this subject the opposing theory suggested that basal drag along the moho drove plat tectonics.

The reasons i support the theory of slab pull is that the densest and thickest part of the oceanic crust is found entering the subduction complex. The plate cools and thickens over time.

There is also a large part of the plate slowly sinking into the outer mantle. The thin part of the plate near mid Oceans ridges would buckle and deform if it were to push plates beneath each other.

Instead what we have is a density gradient where the cool thick oceanic crust partially melts releasing silicone material along plate boundaries as the dense metamorphized rock slowly sinks into the hot super-elastic less dense magma that consumes it.

Here is a supporting reference that uses physics to prove the same point:

http://openlearn.open.ac.uk/mod/resource/view.php?id=172203

Regardless of the specific transfer mechanism though, do we not concur the energy source must be the high-temperature magma?

Well I do not believe that magma has much of a pushing force, whether it be ridge push or basal drag. Areas of increase heat flow, hot spots, do not correlate with increased plate velocities.

I believe that density and tensile strengths associated with slab subduction drive plate tectonics. Ridge push, basal drag, orogenies and other tectonic events are all associated with vectors velocities. There is no single force controlling the dynamic behaviour we observe, it just appears to me that slab pull is the dominant force in play.

Yes, I see where you are coming from, and I'm not disagreeing (or necessarily agreeing). All I'm trying to point out is that there is a source of energy that allows whatever mechanistic process really IS at work (push, pull, leverage, magic wheels, whatever) to cause motion. It's driven by a heat engine, in other words, fueled by the hot magma, and likely assisted by "temperature turbidity" caused by differential heating. Agree?

Yes, and the heat engine is related to gravity and and Earth's core... You can imagine material passing through a solid phase, a long transition through a thick layer of super visco-elastic material on into a plasma.

The cool, dense outer crust releases lighter bouyant material through volcanic arcs as it recrystalizes into a super dense mantle material. The altered basalt or peridotite becomes more dense than the rising magmas. The density gradient creates a slab pull force acting on the thickest part of the plate.

Along the moho I don't believe there is a distinct transition from one phase to another. I also don't see magma moving uniformly beneath these floating plates. Possibly oceans ridges always form near resting mountain belts?

Maybe it is the initial melting of abnormally thick continental plates that allows these convection cycles to form that later feed magma into ocean ridges.

Possibly - I've seen graphic representations of the magma convection (always look too uniform to be realistic) but no solid explanation for the source/cause. It seems there are some rather localized effects, as if the convection currents stay relatively "put" and everything swirls around them. I don't know if that represents reality or not, but it would explain (at least in part) the hot spots that we know exist (like under Hawaii).

OBTW, one of the factors that long-term climatic change could be influenced by is crustal plate shifts. The Gulf Stream is a heat engine (now) that causes a counter-flow of colder, fresher water to flow southward, and with the Atlantic basin growing ever wider, I'm sure that would be influenced. Oh, for a way-back machine to drop some telemetering sensors every few hundred thousand years ago, eh?

If we could retro date instrumentation, some valuable data would come from understanding what happened to the thermohaline circulation in the Younger Dryas. Maybe if we could observe sudden shifts in ocean currents we could then better theorize the dynamics of plate tectonics. Its always so hard to build proof when you are lacking raw data.

Besides, minus a few phase changes the most analogous system to plate tectonics would be the thermohaline circulation, n'est pas?

The system of what drives the tectonic plates is easily and logically worked out:

It cannot be "The weight of a sinking Plate", because before plates meet, nothing has sunk, yet they still approach, being driven from the rear, like a horse in a chariot, getting the whip.

So, it is the localised hotspot, along a thinning portion of seafloor crust, which upwells, then the cooling of the hot plate edge, which welds to the rear of the plate as it cools, thus leaving a central gap for further upwelling, and the cycle repeats.

At the frontal edge of a tectonic plate, it is just the blade of the tectonic bulldozer, being pushed from the mid-oceanic ridge upwelling heat/welding/cooling/further upwelling system.

As far as I can see, if the plates are large enough, and there is sufficient continental crust, for the Indian/Asian collision, the movement will continue as I said in an earlier Post: http://cr4.globalspec.com/comment/249755/Re-Geologists-Study-China-Earthquake-For-Glimpse-Into-Future also here:http://cr4.globalspec.com/comment/251830/Re-Geologists-Study-China-Earthquake-For-Glimpse-Into-Future

There is another point to remember, that as the Planet Earth cools, it must also shrink, due to cooling contraction, and thus cracking and deformation of the rocky crust shall continue into the foreseeable future.

Kind Regards....

The oceanic plate sinks rather deep into a trench before it makes content with the opposing continental plate. crustal contamination, as found in the Yuan de Fuco Plate causes bouyancy and resistance to subduction. Topography is highest near the ridge where the plate is at a minimal thickness and lowest near the trench. Density is key to the process.

The process you describe is theorized as basal drag. Most geologist accept this as a plausible force, but undeniably slab pull has been named the dominant force driving plate tectonics.

As for an MOR (Mid-Ocean Ridge), it may not be as simple as you put it. you Have flowing pillow lavas that reach the surface. This forms over sheeted dikes that were once a pathway for the lavas to reach the surface. Thick layers of Gabro and then Peridotite accumulate beneathe plate as the lavas cool.

The idea that density drives this process explains the rapid movement of oceanic plates in the Pacific Ocean, an understaning of why at times we observed subduction roll-back and describes why some plate resisting subduction due to crustal contamination are destined to correlate with significant tectonic events.

As for your statement,

As far as I can see, if the plates are large enough, and there is sufficient continental crust, for the Indian/Asian collision, the movement will continue

That couldn't be any further from the truth. Bouyant crustal material acts as a dampening force. Light silicates will not sink into the lithosphere. How do you not see the correlation between the Adirondack mountains and the Himalayas? The Eurasian plate is destined to consume the Indian Plate that is dwarfed in size comparison.

It's admittedly little more than a suspicion on my part, although an informed one, but I think the process is dynamic enough to be run by both methods working in combination. The pushme-pullyu is at work down there...